Nitrone spin traps and their pyrrolidine analogs in myocardial reperfusion injury : hemodynamic and ESR implications

Abstract

Formation of free radicals during reperfusion of the isolated ischemic heart has often been demonstrated by detecting hydroxyl radical spin adducts of the nitrone 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in coronary effluents. However, questions still remain regarding (a) whether the reported cardiovascular effects of nitrone perfusion may affect the formation of spin adducts, and (b) the primary generation of superoxide (Oᠨ Ϫ 2 ), because of the short persistency of Oᠨ Ϫ 2 /DMPO spin adduct. We therefore compared the effects of perfusing 5 mM of two nitrones, DMPO and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide (DEPMPO) or the two structurally related pyrrolidines, diethyl (2-methyl-2-pyrrolidinyl) phosphonate (DEPMPH) and pyrrolidine (PyH), on postischemic functional recovery of rat hearts subjected to 10 min of low-flow ischemia, 30 min of global ischemia and 60 min of reperfusion. All compounds were added to the perfusate before ischemia, throughout low-flow ischemia and during the initial 10 min of reflow. In one additional group, hearts received DEPMPO only at reflow. Hemodynamic and in vitro ESR evidence is presented indicating that the phosphonate group of DEPMPO and DEPMPH confers these molecules with an enhanced cardioprotective efficacy, unrelated to radical scavenging, acting in synergy with the intrinsic radical trapping effects of the nitronyl group. Continuous-flow ESR spin trapping using 5.7 mM DEPMPO administered at reflow, but not before ischemia, demonstrated for the first time extended formation of Oᠨ Ϫ 2 in the reperfused myocardium.Keywords : ischemia/reperfusion injury; superoxide; continuous-flow ESR; spin trap ; functional recovery.The formation of oxygen-centered free radicals such as su-ing to the very short life-span of oxyradicals under physiological conditions, two main ESR strategies for their detection and peroxide (Oᠨ Ϫ 2 ) and hydroxyl radical (HOᠨ) is a well-established phenomenon occurring during myocardial ischemia/reperfusion. quantitative analysis have been developed in cardiovascular studies. These highly reactive species have been incriminated in the pathogenesis of reperfusion-induced electrophysiological and First, ESR studies at the temperature of liquid nitrogen (freeze trapping) showed that the normal free radical content of biochemical disturbances leading to ventricular fibrillation and tissue necrosis [1Ϫ3]. Over the last decade, ESR spectroscopy cardiac tissue is markedly altered after an episode of ischemia/ reperfusion [4Ϫ9]. Plausible explanations for the origin of these has been extensively used to characterize post-ischemic free radical formation in isolated heart models or in intact animals. Ow-changes have been proposed, including a modification in the redox state of some proteins involved in the mitochondrial respi- tissue samples must be stringently controlled to avoid the formaAbbreviations. DMPO, 5,5-dimethyl-1-pyrroline N-oxide; DMPOtion of artifactual signals and it is therefore admitted that freeze OOH, 2,2-dimethyl-5-hydroperoxy-1-pyrrolidin...

Neuroprotective antioxidant STAZN protects against myocardial ischemia/reperfusion injury

“…The nitrone moiety can be incorporated into molecules with different structures and still maintain its ability to combine with reactive free radicals to yield more stable nitroxide products and provide therapeutic neuroprotection [18] and cardioprotection [19]. The STAZN molecule, which contains two nitrone moieties attached to azulene groups, was designed to have greater antioxidant potency and lipophilicity than other nitrones, in order to inhibit lipid peroxidation more effectively [9].…”

The Radical Trap 5,5-Dimethyl-1-PyrrolineN-Oxide Exerts Dose-Dependent Protection against Myocardial Ischemia-Reperfusion Injury through Preservation of Mitochondrial Electron Transport

“…1) have exhibited pharmacological activity, such as in the treatment of neurodegenerative disease and acute stroke (Floyd et al, 1997;Floyd and Hensley, 2000). Several groups have evaluated the use of DMPO as a potential cardioprotective agent against myocardial ischemia/reperfusion injury (Tosaki and Braquet, 1990;Bradamante et al, 1993;Pietri et al, 1998;Maurelli et al, 1999).…”

“…However, the slow reactivity of DMPO with O 2 . and the low efficiency of spin trapping led investigators to use high-spin trap concentrations from 5 to 40 mM (Bradamante et al, 1993;Pietri et al, 1998;Maurelli et al, 1999). Administration of DMPO during the preischemic period or during reperfusion was assumed inconsequential in determining the extent of left ventricular (LV) functional recovery (Hearse and Tosaki, 1987;Bolli et al, 1989;Pietri et al, 1998).…”

“…Conflicting studies have been reported in regards to the mode of DMPO action although spin trapping of free radicals may be the most plausible mechanism for its cardioprotective property against reperfusion injury. Bradamente et al (1993) showed that DMPO in millimolar concentrations did not show cardioprotection from ischemia-reperfusion injury using Langendorff rat heart preparations, but Pietri et al (1998) and reported protection. Moreover, 1,2,2,4,5,5-hexamethyl-3-imidazoleine-oxide (HMIO) (Tosaki et al, 1992) or pyrrolidine (PyH) (Pietri et al, 1998) (Fig.…”

“…Bradamente et al (1993) showed that DMPO in millimolar concentrations did not show cardioprotection from ischemia-reperfusion injury using Langendorff rat heart preparations, but Pietri et al (1998) and reported protection. Moreover, 1,2,2,4,5,5-hexamethyl-3-imidazoleine-oxide (HMIO) (Tosaki et al, 1992) or pyrrolidine (PyH) (Pietri et al, 1998) (Fig. 1), which are structurally related compounds but not spin traps, did not exhibit improvement in cardiac function, further confirming the role of the nitrone moiety in cardioprotection.…”